THOMPSON: METAMORPHOSES OF HERMIT CRAB. 171 
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Decapods show that in the Thalassinid, Calliaxis, and the shrimp, 
Crangon, the hepatic arteries, although appearing in the zoea phase, 
are yet later in development than the antennary arteries. Thus the 
latter in their development seem to precede the hepatics when both 
pairs are not present throughout larval life. And in Eupagurus the 
antennary arteries appear unusually late, not until the fourth zoea. 
Unquestionably, the ventral thoracic artery does not enter the 
abdomen at any stage, but as already noted, this vessel was difficult 
to trace and the distribution of its branches could not be completely 
determined. It is certain, however, that in the first zoea, vessels pass 
off to the first maxilliped; that in the second zoea this artery sup¬ 
plies the third maxilliped and, in some cases at least, one or more of 
the rudimentary limbs; and in the fourth stage the artery extends 
to the mouth and gives off branches to the maxillipeds and to the 
five pairs of rudimentary limbs. It is only necessary to suppose that 
the artery gives off in addition to the branches already enumerated, 
vessels to the second maxilliped in the first, and to the two pairs of 
anterior maxillipeds in the second zoea, to make the arrangement for 
each stage agree exactly with the distribution of the vessels in the 
“Pagurus” zoeae studied by Claus (’ 84 ). The ascending arte¬ 
rioles which pass up through the nerve chain between the ganglia 
for the first and second limbs and in the next posterior interspace 
(Bouvier, ’ 89 , ’ 91 ) are discernible as early as the second zoea. Two 
other ascending arterioles are found even in mature glaucothoe: 
one between the maxillipedal and the clieliped ganglia and one 
between the maxillipedal and the maxilla ganglia. They may yet be 
detected in the adult. Some sections of zoeae suggest the possibility 
of the existence during the earlier stages, of additional ascending 
arterioles between the individual maxillipedal and maxilla ganglia, 
but they are not conclusive. 
The superior abdominal artery is present throughout the develop¬ 
mental period. With the earlier zoea it is a simple vessel extending 
almost the length of the abdomen in the first, and to the telson in 
the later stages. In the fourth zoea and glaucothoe, however, this 
artery gives off five pairs of segmental branches, a pair for each seg¬ 
ment from the second to the sixth. 
At the time when the livers commence their shift, the adult plan 
is evolved from this simpler arrangement (pi. lU, fig. 64). A new 
artery arises from the right segmental artery in the second segment, 
